1. Field of the Invention
The present invention is associated with the development of a novel combined immunogenic peptide vaccine against PCSK9 derived from a combination of two different PCSK9 epitopes linked to an immunogenic carrier. The vaccine is established for the prevention and/or treatment of health disorders, caused by the hyperlipidemia, hypercholesterolemia and atherosclerosis.
2. Description of Related Art
Hyperlipidemia, hypercholesterolemia, hypertension and atherosclerosis are cardiovascular disorders considered as leading factors for the worldwide lethality. Together with factors such obesity, diabetes, smoking and lack of physical activity major factors for the development of cardiovascular alterations are genetic disorders such as autosomal dominant hypercholesterolemia (ADH). ADH is considered as an important factor for the development of cardiovascular disorders and is manifested by impaired cholesterol metabolism and increased levels of low density lipoprotein cholesterol, which subsequently leads to the formation of premature coronary artery disease (CAD).
It is known that three major genetic alterations could cause the development of ADH. The classical form of ADH is caused by mutations in the low density lipoprotein receptor (hereafter called LDLR). In addition, mutations in the apolipoprotein B-100 (apoB-100) and more specifically in its ligand-binding domain disrupt the binding of the ApoB-100 to LDLR, which subsequently leads to impaired cholesterol metabolism. Finally, the third and most recently discovered element which by genetic alterations could be involved in the development of the ADH is the proprotein convertase subtilisin/kexin type 9 (hereafter called PCSK9).
PCSK9, also known as neural apoptosis-regulated convertase 1 (NARC-1), is a proteinase K-like subtilase identified as the ninth member of the secretory subtilase family. The PCSK9 protein is synthesized as a ˜72 kDa proprotein, which undergoes autocatalytically cleavage between the prodomain and catalytic domain leading consequently to the generation of the mature protein form. The prodomain (˜14 kDa) remains bound to the mature protein 63 kDa and in this form the mature protein is proceeded towards the secretory pathway.
The role of PCSK9 in the lipid homeostasis is already well known. Not only that the expression of PCSK9 is regulated by the Sterol-Regulatory Element Binding Protein (hereafter called SREBP) in a similar manner to other SREBP-responsive genes involved in lipid homeostasis. But PCSK9 is also involved in the low density lipoprotein cholesterol (hereafter called LDLc) clearance by promoting LDLR internalization and degradation.
In vitro and in vivo studies highlighted the essential role of PCSK9 in the low density lipoprotein cholesterol uptake from the blood. On one side PCSK9 adenovirus overexpression significantly increased the levels of circulating LDLc, and on the other side PCSK9−/− mice showed a 2.8 fold increase in the levels of LDLR and reduction of LDLc compared to wild type animals.
The gene is localized at human chromosome 1p33-p34.3 and is expressed in tissues such as liver, kidney, cerebellum and small intestines. Many studies confirmed that “gain of function mutations” are causing decrease in the LDLR levels and a consequent hypercholesterolemia and predisposition to atherosclerosis. “Loss of function mutations” are increasing the levels of LDLR with a consequent decrease in low density lipoprotein cholesterol (LDLc).
Altogether, PCSK9 regulates LDLR levels posttranscriptionally and therefore is an attractive target for the treatment of atherosclerosis.
Meanwhile, numerous different strategies and approaches have been established to inhibit the function of PCSK9.
Application of siRNA against PCSK9 in monkeys (Macaca fascicularis) led to a significant reduction of total cholesterol. Other investigations with monoclonal and polyclonal antibodies against PCSK9 in mice and non-human primates succeeded to up-regulate LDLR with a concomitant decrease in the levels of total cholesterol and LDLc.
The reduction of PCSK9 levels by monoclonal or polyclonal antibody therapy or inactivation of PCSK9 upon small molecule inhibitors and knock out technology did not show any side effects in different animal models. Therefore, all in all PCSK9 is a very attractive target for the treatment of atherosclerosis.
WO 2011/027257 relates to immunogenic fragments derived from PCSK9 which can be used in a vaccine for the treatment, prevention and alleviation of PCSK9-mediated disorders.
In the WO 2009/100297 antagonists of human PCSK9 are disclosed.
WO 2010/057242 relates to vaccines which comprise peptides derived from a fragment of human PCSK9.